Debt Short Term and Long Term Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Short Term and Long Term Debt [Line Items]
Secured debt	$ 23,386	$ 22,073
Unsecured debt	7,172	6,973
Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	8,983	9,000
Unsecured debt	3,172	2,973
Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	14,403	13,073
Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	4,000	4,000
North America Segment [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	13,355	12,479
Unsecured debt	4,000	4,000
North America Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	2,253	1,678
Unsecured debt	0	0
North America Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	11,102	10,801
North America Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	4,000	4,000
International Segment [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	10,031	9,594
Unsecured debt	3,172	2,973
International Segment [Member] | Revolving Credit Facility [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	6,730	7,322
Unsecured debt	3,172	2,973
International Segment [Member] | Securitization Notes Payable [Member]
Short Term and Long Term Debt [Line Items]
Secured debt	3,301	2,272
International Segment [Member] | Senior Notes [Member]
Short Term and Long Term Debt [Line Items]
Unsecured debt	$ 0	$ 0